Pr Eric E. GabisonOphthalmology · Cornea & refractive · Paris
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Home › Pro area › Corneal dystrophies › Macular dystrophy, or Groenouw type II
Course contents ▾
  1. Introduction & atlas
  2. Anterior dystrophies
  3. Meesmann juvenile epithelial dystrophy
  4. Lisch epithelial dystrophy
  5. Gelatinous drop-like dystrophy
  6. Cogan dystrophy
  7. Reis-Bücklers dystrophy
  8. Thiel-Behnke dystrophy
  9. Stromal dystrophies
  10. Lattice dystrophy
  11. Granular dystrophy
  12. Macular dystrophy, or Groenouw type II
  13. Schnyder crystalline dystrophy
  14. François fleck dystrophy, or "fleck corneal dystrophy"
  15. Posterior amorphous corneal dystrophy
  16. Endothelial dystrophies
  17. Posterior polymorphous corneal dystrophy
  18. CHED
  19. Fuchs dystrophy
  20. Synthesis
  21. Tables & references
Stromal dystrophies

Macular dystrophy, or Groenouw type II

Cues: AD/AR inheritance · graft recurrence +++ high ++ intermediate + low · bold = key terms · Differential diagnosis (blue) and Treatment (amber) boxes.

There are three types of this dystrophy:

  • Type I: the most prevalent form, with an absence of antigenic keratan sulphate throughout the body (cornea, serum, and cartilage). These patients have normal production of dermatan sulphate. Deficient production of keratan sulphate. Serum (-), cornea (-), keratocytes (-).
  • Type IA: keratan sulphate antigen positive in the corneal keratocytes (intracellular) but not in the extracellular compartment or serum. Serum (-), cornea (-), keratocytes (+).
  • Type II: normal keratan sulphate to dermatan sulphate ratio. Quantitative abnormality (30% less than normal) and qualitative abnormality (40% shorter than normal). Serum (+), cornea (+), keratocytes (+).
  • Keratan sulphate ELISA may help in the diagnosis of macular dystrophy, even at a subclinical stage.
Genetics
AR Autosomal recessive (AR), the least common of the 3 dystrophies (granular and lattice)
Mutation
non-TGFBI, 16q22.1, N-acetylglucosamine 6-O-sulfotransferase (CHST6).
Laterality
Bilateral
Symmetry
Yes
Systemic factors
Abnormal keratan sulphate production.
Age of onset
From adolescence, sometimes even earlier, as a bilateral corneal abnormality appearing between the ages of 3 and 9 years.
Location
The entire stroma; pachymetry is low.

Appearance:

Direct illumination
gray-white deposits, initially in the anterior stroma and poorly defined, progressing to affect the entire stroma and even reaching the endothelium (guttata) and extending toward the limbus. They take on a poorly defined macular appearance. The stroma between the blurred macular deposits is not transparent. The deposits are superficial and prominent centrally and discrete and deep as they approach the limbus.
Retroillumination
The deposits appear opaque
Pain or recurrent erosion
rare
Visual acuity
deteriorates rapidly and becomes severely impaired around the 3rd and 4th decade. Patients often present with decreased visual acuity. Photophobia may be greater than would be expected from the clinical examination.

Diagnosis:

  • Histology: deposits of glycosaminoglycans (GAG), mucopolysaccharide (non-sulphated keratan sulphate), both intracellular (keratocytes and even endothelial cells), within the endoplasmic reticulum (not at the lysosomal level as in the mucopolysaccharidoses), and extracellular between the stromal lamellae. Staining with Alcian blue, PAS, and colloidal iron throughout the full thickness of the cornea.
  • A dystrophy due to a disorder in the metabolism of stromal GAG within the keratocytes, causing deficient secretion of keratan sulphate and, conversely, accumulation of the other proteoglycans.
  • Electron microscopy: positive staining for GAG within the keratocytes and endothelium as well as in the cellular matrix, in the form of fibrogranular material. The anterior part of Descemet membrane is normal, whereas the posterior part is infiltrated by vesicular and granular material originating from the abnormal endothelial cells.
  • Confocal microscopy: blurred, slightly hyperreflective material, mainly in the anterior stroma, with a striated appearance.
  • OCT: the deposits produce poorly defined stromal hyperreflectivity with an irregular and wavy stromal surface
  • The cornea is thinner than normal, with the presence of endothelial guttata and hypoesthesia.
Differential diagnosis
  • With the granular form, though the following features help in the diagnosis:
  • Recessive nature of the disorder
  • Corneal thickness
  • Involvement reaching the limbus
  • Involvement extending throughout the entire stroma
  • Stromal haze between the deposits from an early age
  • With the systemic mucopolysaccharidoses:
  • These are usually localized GAG deposits within the cornea, compared with systemic deposits secondary to generalized abnormalities of mucopolysaccharide production or degradation.
  • The deposits occur within the endoplasmic reticulum in macular dystrophy, whereas they occur within the lysosomes in the mucopolysaccharidoses.
  • Corneal involvement in the systemic forms differs from that of the corneal dystrophy, because the involvement is mainly epithelial and spares the endothelium.
Treatment

Treatment of recurrent corneal pain (keratalgia):

  • Medical (contact lenses, artificial tears, tetracyclines)

Once decreased visual acuity is present, treatment varies according to the depth of the deposits (rare before the age of 50):

Recurrence + Recurrence on the graft: Slower than in the TGFBI+ dystrophies.